Videos, music, and other types of audio video (“AV”) media are conventionally sold to consumers through stores or mail-order companies. When AV media are sold through these types of outlets, the media are usually distributed on tangible media, such as digital video disks (“DVDs”), Blu-Ray disks, digital tapes, and so on. Another, alternative way of distributing AV media is to receive orders and to distribute, e.g., videos, electronically over a communications network, such as the Internet. A person can connect to a media provider and download AV media over the Internet, either for free or for a fee.
The downloaded video can be played back with appropriate AV playback software on the user's computer, either while the computer is connected to the Internet (that is, through streaming playback of the AV files) or at later time. Examples of common software for playing AV files include the RealPlayer™ and the Windows™ MediaPlayer™ software. The user may organize his or her downloaded AV files on his computer. The user may also optionally transfer the downloaded AV files from his computer to a portable player that can play back AV files, so that he can leave his computer and still be able to view the previously downloaded AV files. Alternatively, the AV file can be downloaded directly to a user's portable device, such as a tablet or smart phone.
When one buys AV media stored on a tangible medium, such as a disk, the purchaser gets unlimited rights to play back the video content for his personal use. AV media that are provided through digital delivery to a playback device can have an associated expiration, such as time-limited playback rights, or rights that allow a user to play the AV files only a certain number of times. A user may therefore select AV media for a playback device and view the selected video during a certain time period or for a certain number of times for a smaller fee, or even for free, compared to what he would have paid if the video were stored on a tangible medium. If the user after this time likes the video, he can choose to refresh the expiration of the video and obtain new playback rights.
A problem with time-limited playback is that users may change internal clocks on playback devices that are used to keep track of the expiration times for content or may even hack the software that reads this local time clock. As a consequence, the time limitation imposed by the AV provider will not work, and the AV providers will have little interest in providing AV files for a reduced fee compared to the fee for unlimited playback. It is therefore likely that content providers would offer a more limited service or charge higher prices than what would be necessary if there were a way to guarantee that users could not manipulate the imposed expiration limitations on the AV files, leaving potential customers with less than a full range of options to choose from.